Answer: a) are in the experimental group
Explanation: When testing the effectiveness of a new drug, there is usually an experimental group and a control group.
The experimental group consists of individuals that are randomly selected and are then given the drug. Their reaction to the drug is recorded to measure how well it treats the illness it is supposed to cure, in this case the common cold.
The control group is created to monitor a situation where the independent variable, in this case, the new drug, is not involved. In drug studies, the people in this group are given a placebo which looks like a drug but has no active ingredient.